Founded in 1993 by brothers Tom and David Gardner, The Motley Fool helps millions of people attain financial freedom through our website, podcasts, books, newspaper column, radio show, and premium investing services.

Under Armour has reported incredible growth across the board this year -- but one segment in particular has stood out, and it's the one that has the most room left to run.

Under Armour(NYSE:UAA)(NYSE:UA) seems to be firing on all cylinders lately. Each of its segments grew substantially in the most recent quarter to give it an overall 28% sales growth year over year. But while apparel and other segments are each performing well, footwear is what's leading its impressive growth. With the company investing in new styles and innovations, this segment is likely to continuing outperforming the others for some time.

A brand of madness

Back in 2008, a Bloomberg article questioned the whole idea of the company competing in footwear: "Is Under Armour mad for challenging Nike and Adidas in sneakers? After all, Nike in particular can outspend UA 10 to 1 in advertising, not to mention its capacity to cut prices to push volume," wrote David Kiley.

Eight years later, Under Armour's quarterly footwear sales have grown by about 426%, from $46 million in Q2 2008 to $242 million in Q2 2016. Under Armour's share of the global athletic shoe market (1.5%) is still just a fraction of NIke's (23%), but its growing quickly.

In the recent quarter, Under Armour's footwear sales grew 58% year over year, compared with 19% growth for apparel, and 21% in accessories. The only segment to grow faster was connected fitness at 73%, though that total revenue, at $23 million, is still just a sliver of sales.

Under Armour Sales

Segment

Q2 2016

Q2 2015

Growth

Apparel

$613 million

$515 million

19%

Footwear

$243 million

$153 million

58%

Accessories

$101 million

$83 million

21%

Connected Fitness

$24 million

$13 million

73%

Other

$21 million

$18 million

16%

Total

$1.002 billion

$784 million

28%

Under Armour attributes much of its recent footwear success to its well-performing basketball shoes, but running, training, golf, and other styles are each seeing their own successes, thanks both to well-received styles and increased average selling prices.

Basketball shoe sales lead the way

The Under Armour "Chef" Curry 2 shoes that made a splash in internet meme's. Photo: Under Armour

Remember the all-white Curry 2 Low "Chef Curry" basketball shoes that Under Armour got grilled for on social media, where they were derided as "grandpa shoes" and worse? Turns out they were some of Under Armour's best-selling products of the most recent quarter, selling out online within five weeks.

In the months since Under Armour-sponsored Steph Curry won his second consecutive NBA MVP title, its basketball shoes have led footwear sales growth. "Sales of Curry footwear have been extremely strong, and with the Curry 3 coming this fall, we are anticipating our business will continue to post incredible growth," CEO Kevin Plank said during the recent earnings call.

Basketball shoes are also helping Under Armour grow its brand in China, where basketball is gaining in popularity. "Stephen Curry's growing global awareness continues to help drive our business in greater China," said Plank. "The social media impressions for Stephen during the NBA playoffs reached over 2.7 million during that time, and helped drive extremely high sell-through rates in the Curry 2 throughout the first six months, making it our top-selling item in China year to date."

The run category is sprinting ahead

Running is another category focus of Under Armour. Its Speedform line, which uses a single-mold heel cup that replaces the traditional sole insert (a change inspired by bra manufacturing) has helped the company gain traction in the running market. The Gemini 2 Record Equipped, which includes a chip that connects the shoe to the wearer's MapMyRun app, launched in Q1 and has helped to give Under Armour a technological leg up in the footwear game as well.

Runner wearing a pair of Gemini 2 Record Equipped. Image Source: Under Armour

Running is an important category for Under Armour broadly -- it has apparel, accessory, and connected fitness offerings that can appeal to all levels of runner, and the sport is one with a low barrier to entry for casual athletes. As Under Armour continues to promote itself as providing the most innovative performance gear, it needs running shoes that live up to the hype. So far, the Speedform line seems to be doing that well.

Even more expansion of the footwear

While basketball and running are the two segments garnering the most attention now, Under Armour is not asleep at the wheel -- it's diversifying to other types of footwear as well. Among its interesting recent footwear releases was the first 3D-printed cross-trainer -- the UA Architech, which had an extremely limited 96 pair release that sold out in just 19 minutes. That line is expected to have another launch later this year.

Under Armour's new golf shoe. Image: Under Armour

Under Armour also launched its first ever golf shoe this year, which pro-golfer Jordan Speith wore during the Masters Tournament, where he finished second overall. And the company is preparing to launch Under Armour Sportswear (UAS) this fall, which is athletic-inspired casual wear that is sure to include some new shoe styles.

$1.7 billion in footwear sales within 2 years?

Canaccord analyst Camilo Lyon, who sees footwear as a compelling part of Under Armour's long-term appeal for investors, gives Under Armour stock a buy rating and price target of $65 (about a 50% upside from Aug. 16). In a recent report, Lyon wrote: "We expect the 50%+ growth in footwear to continue for the foreseeable future, as new product intros across running (Slingshot, SpeedForm Gemini 2 RE, UA Architect), basketball (Curry 3.0 is scheduled for a fall release) and golf have been well received boding well for future releases."

Last September Under Armour forecast it would deliver $1.7 billion in footwear sales by fiscal year 2018. That would be about 2.5 times the $678 million it reported in 2015. However, with growth like this segment has experienced so far, and with so many new styles and innovations coming down the pipeline, hitting that goal looks entirely possible.

Seth McNew owns shares of Nike, Under Armour (A Shares), and Under Armour (C Shares). The Motley Fool owns shares of and recommends Nike and Under Armour (A Shares). The Motley Fool owns shares of Under Armour (C Shares). Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.